CO-PROX Reaction over Co3O4|Al2O3 Catalysts—Impact of the Spinel Active Phase Faceting on the Catalytic Performance

Grzybek, Gabriela; Ciura, Klaudia; Gryboś, Joanna; Indyka, Paulina; Davó‐Quiñonero, Arantxa; Lozano‐Castelló, Dolores; Bueno‐López, Agustín; Kotarba, Andrzej; Sojka, Zbigniew

doi:10.1021/acs.jpcc.9b03025

Cited by 35 publications

(15 citation statements)

References 61 publications

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“…Several previous reports have demonstrated that the surface oxidation state of cobalt plays a key role for COPrOx reactivity. ,, At low temperatures, the COPrOx mixture can oxidize metallic cobalt, whereas at relatively high temperatures, cobalt oxides could be reduced back to metal. ,, Thus, depending on the COPrOx reaction conditions, cobalt may easily swap between different oxidation states. Herein, synchrotron-based NAP-XPS and NEXAFS were used to monitor, on a comparative basis, the surface oxidation state of CoO x and CoVO x during the COPrOx reaction.…”

Section: Resultsmentioning

confidence: 99%

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

et al. 2021

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Preferential oxidation of CO (COPrOx) is a catalytic reaction targeting the removal of trace amounts of CO from hydrogen-rich gas mixtures. Non-noble metal catalysts, such as Cu and Co, can be equally active to Pt for the reaction; however, their commercialization is limited by their poor stability. We have recently shown that CoO is the most active state of cobalt for COPrOx, but under certain reaction conditions, it is readily oxidized to Co3O4 and deactivates. Here, we report a simple method to stabilize the Co 2+ state by vanadium addition. The V promoted cobalt catalyst exhibits considerably higher activity and stability than pure cobalt. The nature of the catalytic active sites during COPrOx was established by operando NAP-XPS and NEXAFS, while the stability of the Co 2+ state on the surface was verified by in situ NEXAFS at 1 bar pressure. The active phase consists of an ultra-thin cobalt-vanadate surface layer, containing tetrahedral V 5+ and octahedral Co 2+ cations, with an electronic and geometric structure that is deviating from the standard mixed bulk oxides. In addition, V addition helps to maintain the population of Co 2+ species involved in the reaction, inhibiting carbonate species formation that are responsible for the deactivation. The promoting effect of V is discussed in terms of enhancement of CoO redox stability on the surface induced by electronic and structural modifications. These results demonstrate that V-promoted cobalt is a promising COPrOx catalyst and validate the application of in situ spectroscopy to provide the concept for designing better performing catalysts.

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Section: Resultsmentioning

confidence: 99%

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

et al. 2021

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“…The temperature range also matches that generally observed for the reduction of the Co3O4 spinel phase. 32,33 It is thus attributed to the reduction of Co3O4 crystallites. In fact, the narrow profile is very similar to that of unsupported 3D Co3O4, 32,33 CoNO3/graphene, respectively.…”

Section: Characterization Of Graphene-supported Cobalt Oxides From Thmentioning

confidence: 99%

“…32,33 It is thus attributed to the reduction of Co3O4 crystallites. In fact, the narrow profile is very similar to that of unsupported 3D Co3O4, 32,33 CoNO3/graphene, respectively. The calcined CoNO3-derived composite exhibits a maxima at 380°C, which is similar to the calcined composite derived from the Pc route, with two shoulders at 330°C and 450°C.…”

Section: Characterization Of Graphene-supported Cobalt Oxides From Thmentioning

confidence: 99%

Graphene-supported 2D cobalt oxides for catalytic applications

et al. 2021

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“…The spectra of Co 2p show two asymmetric peaks which can be assigned to Co 2p3/2 and Co 2p1/2 together with corresponding satellite structures. The deconvolution of these spectra revealed the presence of several overlapping features associated to Co 3+ (780.1 ± 0.6 and 795.4 ± 0.6 eV) and Co 2+ (781.7 ± 0.7 and 797.3 ± 0.7 eV) [53]. The observed satellite peaks are typical for spinel structures consists of 3+ cations occupy octahedral lattice sites, filled t 2g and empty e g levels, and 2+ cations in tetrahedral sites [54].…”

Section: Physicochemical Characterization Of Catalysts 321 Xrf Tgmentioning

confidence: 99%

Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media

et al. 2021

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One of the practical efforts in the development of oxygen reduction reaction (ORR) catalysts applicable to fuel cells and metal-air batteries is focused on reducing the cost of the catalysts production. Herein, we have examined the ORR performance of cheap, non-noble metal based catalysts comprised of nanosized mixed Fe-Co spinels deposited on N,S-doped mesoporous carbon support (N,S-MPC). The effect of the chemical and phase composition of the active phase on the selectivity of catalysts in the ORR process in alkaline media was elucidated by changing the iron content. The synthesized materials were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Detailed S/TEM/EDX and Raman analysis of the phase composition of the synthesized ORR catalysts revealed that the dominant mixed iron-cobalt spinel is accompanied by minor fractions of bare cobalt and highly dispersed spurious iron oxides (Fe2O3 and Fe3O4). The contribution of individual phases and their degree of agglomeration on the carbon support directly influence the selectivity of the obtained catalysts. It was found that the mixed iron-cobalt spinel single phase gives rise to significant improvement of the catalyst selectivity towards the desired 4e− reaction pathway, in comparison to the reference bare cobalt spinel, whereas spurious iron oxides play a negative role for the catalyst selectivity.

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CO-PROX Reaction over Co₃O₄|Al₂O₃ Catalysts—Impact of the Spinel Active Phase Faceting on the Catalytic Performance

Abstract: A series of α-alumina supported cobalt spinel catalysts of various exposition of the (100), (111) and (110) planes was synthetized and tested in CO-PROX reaction.

Cited by 35 publications

References 61 publications

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

Graphene-supported 2D cobalt oxides for catalytic applications

Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media

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